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  Low distortion class-d amplifierUSPTO Application #: 20070222507Title: Low distortion class-d amplifier Abstract: A low distortion class-D amplifier. The amplifier comprises a power supply terminal for receiving power, an amplification stage, and an output stage. The amplification stage receives an input signal and generates a ramp signal. Further more, the amplification stage generates a pulse width modulation signal based on the ramp signal and a hysteretic signal. The output stage coupled to the power supply terminal receives the pulse width modulation signal and generates an output. Advantageously, the ramp signal and the hysteretic signal are positioned at a voltage level that is half the voltage level of said power supply and that varies proportionally with said power supply. (end of abstract) Agent: Murabito, Hao & Barnes, LLP - San Jose, CA, US Inventor: Laszlo Lipcsei USPTO Applicaton #: 20070222507 - Class: 330 10 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20070222507. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATIONS [0001]This application claims the benefit of U.S. Provisional Application No. 60/785,105, filed on Mar. 22, 2006, the specification of which is hereby incorporated in its entirety by reference. TECHNICAL FIELD [0002]This invention relates to an amplifier, and more particularly to a low distortion class-D amplifier with high efficiency. BACKGROUND ART [0003]Conventional class-D amplifiers receive an analog input signal and generates a digital output signal. One advantage of a class D amplifier over a linear amplifier (e.g., a class-AB amplifier) is it's high efficiency. Because the output pulses of the class-D amplifier have a fixed amplitude, the switching elements are switched either on or off, rather than operated in linear mode. One common application for a class-D amplifier is a driver for a loudspeaker. [0004]However, most class-D amplifiers that employ standard implementations suffer from propagation delays and low power supply rejection ratio due to the switching waveforms. SUMMARY OF THE INVENTION [0005]The present invention provides a low distortion class-D amplifier. In accordance with one embodiment of the present invention, an amplifier comprises a power supply terminal for receiving a power supply, an amplification stage, and an output stage. The amplification stage receives an input signal and generates a ramp signal. Furthermore, the amplification stage generates a pulse width modulation signal based on the ramp signal and a hysteretic signal. The output stage coupled to the power supply terminal receives the pulse width modulation signal and generates an output. Advantageously, the ramp signal and the hysteretic signal are positioned at a voltage level that is half the voltage level of the power supply and that varies proportionally with the power supply. BRIEF DESCRIPTION OF THE DRAWINGS [0006]Features and advantages of embodiments of the claimed subject matter will become apparent as the following Detailed Description proceeds, and upon reference to the Drawings, wherein like numerals depict like parts, and in which: [0007]FIG. 1 shows a block diagram of a low distortion class-D amplifier, in accordance with one embodiment of the present invention. [0008]FIG. 2 shows a detailed circuit diagram of the low distortion amplifier in FIG. 1 coupled to a loud speaker, in accordance with one embodiment of the present invention. [0009]FIG. 3 shows the waveforms for the hysteretic signal and the ramp signal, in accordance with one embodiment of the present invention. DESCRIPTION OF EMBODIMENTS [0010]Reference will now be made in detail to the embodiments of the present invention. While the invention will be described in conjunction with the embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. [0011]Furthermore, in the following detailed description of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the present invention. [0012]FIG. 1 shows a block diagram of a low distortion class-D amplifier 100, in accordance with one embodiment of the present invention. The class-D amplifier 100 has a high power supply rejection ratio. As shown in FIG. 1, the class-D amplifier 100 comprises a power supply terminal 110 for receiving a power supply VDC, an amplification stage 180, and an output stage 160. [0013]The amplification stage 180 receives an input signal 170 and generates a ramp signal 130. The amplification stage 180 generates a pulse width modulation signal 140 based on the ramp signal 130 and a hysteretic signal 132 that is used to drive the output stage 160. Advantageously, the ramp signal 130 and the hysteretic signal 132 are positioned at a voltage level that is half the voltage level of the power supply VDC and varies proportionally with the power supply VDC. [0014]The output stage 160 coupled to the power supply terminal 110 receives the pulse width modulation signal 140 from the amplification stage 140 and generates an amplified output signal 190. In one embodiment, the output stage 160 comprises a full bridge circuit. [0015]As shown in FIG. 1, the amplification stage 180 comprises a first circuit shown as the translation stage 101 coupled to the full bridge circuit 160 for receiving the input signal 170 and producing a translated signal 120 that is positioned at a voltage level that is half the voltage of the power supply. [0016]The amplification stage 180 further comprises a second circuit shown as the integrating stage 102 that receives the translated signal 120 from the first circuit (translation stage) 101 and an integrating signal 122 from the full bridge circuit 160, and generates the ramp signal 130 therefrom. Therefore, an oscillator and a ramp generator are not needed in the present invention. [0017]A comparison stage 103 receives the ramp signal 130 and the hysteretic signal 132, and generates the pulse width modulation signal 140 to drive the full bridge circuit 160. [0018]To summarize, the amplifier 100 in FIG. 1 comprises a power supply terminal 110 for receiving power; a full bridge circuit 160 coupled to the power supply terminal 110 for providing an amplified output 190; a translation stage 101 coupled to the full bridge circuit 160 for receiving an input signal 170 and producing a translated signal 120 that is positioned at a voltage level that is half the voltage level of the power supply VDC; an integrating stage 102 that receives the translated signal 120 from the translation stage 101 and an integrating signal 122 from the full bridge circuit 160, and generates a ramp signal 130 therefrom; and a comparison stage 103 that receives the ramp signal 130 from the integrating stage 102 and a hysteretic signal 132 from the full bridge circuit 160, and generates a pulse width modulation signal 140 for driving the full bridge circuit 160. Continue reading... Full patent description for Low distortion class-d amplifier Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Low distortion class-d amplifier patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Low distortion class-d amplifier or other areas of interest. ### Previous Patent Application: Op driver with the function of canceling op offset Next Patent Application: Ping-pong auto-zero amplifier with glitch reduction Industry Class: Amplifiers ### FreshPatents.com Support Thank you for viewing the Low distortion class-d amplifier patent info. 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